ZyXEL Communications U-336SA - Manual (Page 149)

Diagnostics & Troubleshooting 135
Trouble Shooting
Your modem is designed to provide years of ultra high speed
satisfaction. In the unlikely event you encounter problems using your
modem, the tips in this section will help you to identify and resolve them.
Most modem problems are a result of incorrect cabling or settings
within your communications or fax software. This section provides a list
of more common problems that you may encounter, followed by likely
solutions.
AT Command Set Problems
Problem
Your modem does not respond to AT commands.
Solutions
1. Make sure the DTR LED is ON. If it is OFF, make sure your
communications software is using the same COM port as your
modem.
2. Check to see that your modem’s COM port is not already assigned
to another installed serial device, such as a mouse or laser printer.
Problem
Your modem fails to execute AT commands.
Solutions
1. Make sure the DTR LED is ON. If it is OFF, make sure your
communications software is using the same COM port as your
modem.
2. You may have omitted the characters AT from the beginning of the
command line. These characters must appear at the beginning of
each command line.